"All you've got to do is compare the size of everyone's rallies," Bennett, who blamed his exit on in-fighting, told CNN. "Donald trump is having ten-, twelve-thousand people show up at rallies, and a lot of these guys are having five or six people show up at their events in Iowa."

Carson, a retired neurosurgeon running as a Republican, briefly eclipsed the New York real estate mogul in polling in November. Yet, amid a series of missteps that culminated in the exit of Bennett and communications director Doug Watts, Carson, a political novice, has faced falling poll numbers while Trump continues to dominate the field.